Abstract Objective: We report a unique case of anatomical variation of the extracranial course of the optic nerve running in the floor of the sphenoid sinus. Method: Clinical and radiological findings are presented. Results: A 39-year-old woman with Turner syndrome presented with severe headache associated with visual disturbances. Magnetic resonance imaging revealed a mass presumed to be a sella meningioma. Computed tomography of the paranasal sinuses was undertaken to help plan surgical removal via an endoscopic trans-sphenoidal approach; this scan revealed an atypical extracranial course of the optic nerve, running in the floor of the sphenoid sinu